“The current cost of ongoing activities in Iraq varies but is about $7.5 million per day based upon a snapshot of operations that have occurred as of Aug. 26,” Pentagon spokeswoman Cmdr. Elissa Smith told NBC News on Thursday. “These include the DoD mission and personnel costs in Iraq to include air operations, and associated enablers such as logistics and intelligence, surveillance and reconnaissance support.”

At that rate, a year of operations would cost $2.7 billion, but the Iraq operations have been relatively light. An accelerated mission to hunt down ISIS — “to the gates of hell,” as Vice President Joe Biden put it — could come with a significantly higher price tag.